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12 votes
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How do I figure out how many monomer configurations I need for my simulation?

tldr; it depends on flexibility / number of rotatable bonds A while ago, I answered a related question - in general, molecules with fewer "rotatable bonds" need fewer conformers geometries ...
Geoff Hutchison's user avatar
9 votes
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Exchange-Correlation Two-Electron Integrals

I assume you're referring to eq 51 of the Hirata-Head-Gordon-Bartlett paper. One should note that these are not two-electron integrals, since there is only one spatial position; these are rather ...
Susi Lehtola's user avatar
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8 votes
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Alternatives to VEDA 4 vibrational energy distribution analysis software?

LocVib (part of MoViPac) I have never used VEDA before, but according to the paper, it decomposes the normal modes into vibrations of atomic groups, bond stretching, bending or something else. ...
Y. Zhai's user avatar
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5 votes

What do the indices mean in an FCIDUMP file?

"I was able to guess most of results, except the ones with value 0.663472." I am able to confirm that your integrals are correct even for the 0.663472 case, because by calculating them ...
Nike Dattani's user avatar
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5 votes
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Computing analytic derivatives of molecular Hamiltonians obtained from solving Hartree-Fock equations

PySCF and Psi4 both implement analytical geometric Hessians for Hartree-Fock calculations. The computation of the geometric Hessian indeed requires solving the coupled perturbed Hartree-Fock equations:...
Susi Lehtola's user avatar
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5 votes
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Calculating first and second derivatives of a molecular Hamiltonian?

The derivatives of a molecular Hamiltonian with respect to nuclear coordinates can be performed analytically (as you correctly pointed out), and therefore does not need PySCF or Psi4, which are ...
Nike Dattani's user avatar
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5 votes
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Error running psi4 on charged molecules

As you already figured out, the error is that the charge and multiplicity are inconsistent with the molecule; this is what Psi4 tells you: qcelemental.exceptions.ValidationError: Inconsistent or ...
Susi Lehtola's user avatar
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5 votes

How do I figure out how many monomer configurations I need for my simulation?

At a rough guess you can assume that the number of conformers you need to generate (N_conf) is directly proportional to the number of rotatable bonds (N_rot) in a given compound. I seem to recall that ...
Michael Brunsteiner's user avatar
4 votes

What do the indices mean in an FCIDUMP file?

I would like to post a partial answer that I have for now. For the indices ijkl in the FCIDUMP file, it corresponds to the integral (see https://theochem.github.io/horton/2.0.2/user_hamiltonian_io....
fagd's user avatar
  • 231
4 votes
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Decay rate of DSD-PBEPBE-D3BJ

I guess the OP is referring to the asymptotic potential which is -1/r with the optimized effective potential (OEP) but which decays exponentially with density functionals as well as Hartree-Fock ...
Susi Lehtola's user avatar
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3 votes

Psi4 Takes too Long to Save Computation Results to Python Notebook

I ran the calculation for ethanol and it took me 0.78 mins. System Specs: ...
Vandan Revanur's user avatar
2 votes

PSI4 SAPT calculation: failure to write

I suspect it turned out to be an issue with scratch space. I moved the scratch location to a local compute node instead of a networked filesystem scratch space. The variable to be set up is $...
bhopshang's user avatar
  • 233
2 votes
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Psi4 functionnals: LDA0

As Tyberius already stated in a comment above, LDA0 is a hybrid functional. However, you can't even expect two different LDAs to give the same results! SVWN5 is different from SVWN3 is different from ...
Susi Lehtola's user avatar
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2 votes
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How do I install the beta5 version of PSI4 on my WebMO Basic server?

I then tried to compute the energy of hexaiodostannate(IV) at the wB97X-2(TQZ)/def2-TZVPPD level of theory wB97X-2(TQZ), published by Chai and Head-Gordon in doi:10.1063/1.3244209 is a double hybrid ...
Susi Lehtola's user avatar
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